JPH0965237A - Video signal processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration an image quality at a boundary between a letter box signal major image part and a non-image part. SOLUTION: When a video signal is a letter box signal or a major image part of the letter box signal, a boundary detection circuit 12 detecting a boundary between the major image part and a non-image part does not provide an output of a discrimination signal. A signal processing circuit 13 uses a delay circuit 14 to conduct addition/ subtraction processing using the correlation of inter-line. A switch 15 selects the signal processing circuit 13 and provides an output. When the boundary detection circuit 12 discriminates the boundary to be an upper boundary, a switch 17 selects an input signal and gives the selected signal to a signal processing circuit 18. The input signal in this case is a major image section signal. When the boundary detection circuit 12 discriminates the boundary to be a lower boundary, the switch 17 selects a signal of the delay circuit 14 and gives the selected signal to the signal processing circuit 18. The signal in this case is a major image section signal being the output of the delay circuit 14. The signal processing circuit 18 does not conduct processing between lines but within one line. The boundary detection circuit 12 controls the switch 15 and an output of the signal processing circuit 18 is selected at a boundary between the major image section and a non-image section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit for performing signal processing without any adverse effect even at a boundary between a non-picture portion and a main picture portion of a letterbox signal.

[0002]

2. Description of the Related Art A conventional two-line luminance (Y) is shown in FIG.
The Y / C separation circuit for separating the color signal (C) and the color (C) signal will be described with reference to FIG. 9 showing the signal waveform of each part in FIG. FIG. 9A shows a signal waveform when a video signal that is not a letterbox signal or a main image portion video signal of a letterbox signal is input, and FIG. 9B shows a main image portion and a non-image portion of a letterbox signal. It is a signal waveform when the boundary of is input.

The video signal input from the input terminal 81 is
The delay circuit 82 having a delay amount of one horizontal period (line) delays one line. The subtractor 83 is used to subtract the output signal of the delay circuit 82 from the input signal. This subtractor 83
The output of is using a bandpass filter (BPF) 84,
The color signal band is limited and the color signal C is output as an output terminal 85.
Output more. The color signal C is subtracted from the input video signal by the subtractor 86, and the luminance signal Y is obtained from the output terminal 87. A normal video signal has a correlation between two lines, which are close to each other, and when the video signals for two lines to be processed are not at the boundary between the main image portion and the non-image portion, the luminance as shown in FIG. Signals and color signals can be separated correctly.

Next, consider the processing at the boundary between the main picture portion and the non-picture portion of the letterbox signal as shown in FIG. FIG.
The (m + 1) line in (b) is the main image portion signal immediately after the non-image portion section. The m line is a non-picture portion signal immediately before the main picture portion section. There is no correlation between the signals, and the output color signal in this case has a gain that is half that of the (m + 1) line color signal component, as shown in C. An output luminance signal Y is obtained by subtracting the obtained output color signal from the input signal. However, since the color signals could not be correctly separated, the color signal components remain in the luminance signal, resulting in dot interference, which deteriorates the image quality.

As described above, at the boundary between the main picture portion and the non-picture portion of the letterbox signal, the conventional Y / C separation circuit cannot provide correct processing. The same can be said not only for such Y / C separation but also for a circuit such as noise reduction or vertical emphasis that performs addition / subtraction processing between lines or fields.

[0006]

In the conventional video signal processing apparatus for adding / subtracting between a plurality of lines or fields, it is possible to perform correct signal processing near the boundary between the main picture portion and the non-picture portion of the letterbox signal. However, there is a drawback that the image quality is deteriorated. The present invention provides a video signal processing device that does not deteriorate the image quality even at the boundary between the main image part and the non-image part of a letterbox signal.

[0007]

In order to solve the above-mentioned problems, according to the present invention, in the case of an input video signal of letterbox format in a video signal processing apparatus for performing addition / subtraction processing between a plurality of horizontal lines or a plurality of fields. A means for detecting a boundary between the main image portion and the non-image portion of the video signal,
When the detection means detects a boundary, it comprises means for controlling so as to perform signal processing only on the main image portion. With such a configuration, the border detecting means outputs the determination signal at the border between the main image portion and the non-image portion which are located at two upper and lower portions of the screen of the letterbox signal. During the period in which the determination signal is supplied, by processing only the main image portion signal, it is possible to obtain a video signal that does not deteriorate the image quality even at the boundary between the main image portion and the non-image portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram for explaining one embodiment of the present invention. Input terminal 1
If the signal input to 1 is a video signal that is not a letterbox signal or a main image portion of a letterbox signal, the border detection circuit 12 that detects the border between the main image portion and the non-image portion does not output a determination signal, Normal processing is performed using the processing circuit 13. The signal processing circuit 13 uses the delay circuit 14 to perform addition / subtraction signal processing using the correlation between one line (or one field). In this case, the switch 15 selects the output of the signal processing circuit 13 and outputs it from the output terminal 16.

Next, at the boundary between the main picture part and the non-picture part of the letterbox signal where the input signal is located at two positions above and below the screen,
The boundary detection circuit 12 outputs a determination signal. When the boundary detection circuit 12 determines that the boundary is the upper boundary, the switch 17 selects the input signal and inputs it to the signal processing circuit 18. The input signal at this time is the main image portion signal. Boundary detection circuit 12
When it is determined that is the lower boundary, the switch 17 selects the output of the delay circuit 14 and inputs it to the signal processing circuit 18. The output signal of the delay circuit 14 at this time is the main image portion signal. The signal processing circuit 18 does not perform processing between lines (or between fields), but performs processing within one line.
The boundary detection circuit 12 also controls the switch 15, and selects the output of the signal processing circuit 18 at the boundary between the main image portion and the non-image portion and outputs it from the output terminal 16.

The boundary detection circuit 12 may detect the boundary between the main image portion and the non-image portion of the letterbox signal, and further detect whether it is the upper boundary or the lower boundary.
The circuit configuration does not matter.

In this embodiment, since there is no correlation between the signals at the boundary between the main picture portion and the non-picture portion of the letterbox signal, processing is not performed between lines or fields. By switching the processing at the boundary between the main image portion and the non-image portion, erroneous signal processing can be performed and signal processing without image quality deterioration can be performed.

The first embodiment of the present invention will be described with reference to the circuit configuration diagram of FIG.
Another embodiment will be described. The input signal (n + 1) input to the input terminal 21 is input to the delay circuit 22, which outputs the signal n delayed by one line period. The signal n is
The signal is input to the delay circuit 23 and a signal (n-1) delayed by one line period is output.

When the input signal is a video signal which is not a letterbox signal or the main picture portion of a letterbox signal, the boundary detection circuit 24 does not output a determination signal. In this case, 3
The line signal processing circuit 25 has (n + 1), n, (n-1)
The normal addition / subtraction signal processing is performed by using the correlation between the signals of the future, present, and past three lines. At this time, the switch 26 selects and outputs the output of the 3-line signal processing circuit 25.

When the input signal is the boundary between the main image part and the non-image part of the letterbox signal at the two upper and lower parts of the screen, the boundary detection circuit 24 outputs a determination signal. When the boundary detection circuit 24 determines that the boundary is the upper boundary, the switch 27 selects the input signal (n + 1) and inputs it to the 2-line signal processing circuit 28. When the boundary detection circuit 24 determines that the boundary is the lower boundary, the switch 27 outputs the output signal (n-1) of the delay circuit 23.
Is input to the 2-line signal processing circuit 28. The 2-line signal processing circuit 28 uses the current signal n and the switch 27.
2 line signal processing is performed with the output of. That is, when one line of the three lines is a signal of the non-image part, the addition / subtraction signal processing is performed on the remaining two lines of the main image part. The boundary detection circuit 24 also controls the switch 26, and when the boundary between the main image portion and the non-image portion is 2
The output of the line signal processing circuit 28 is selected, and the output terminal 29 is selected.
Output more.

The boundary detection circuit 28 may detect the boundary between the main image part and the non-image part of the letterbox signal, and further detect whether it is the upper boundary or the lower boundary.
The circuit configuration does not matter.

In this embodiment, since there is no correlation between the main image portion and the non-image portion of the letterbox signal, the signal has no correlation.
Do not perform normal processing using lines. At the boundary, processing is performed using two lines of the main image portion having a correlation among the three lines. By switching between 3-line signal processing and 2-line signal processing at the boundary between the main image portion and the non-image portion, it is possible to perform signal processing without image quality deterioration without performing erroneous signal processing.

Next, referring to the circuit configuration diagram of FIG. 3 applied to the Y / C separation circuit, regarding the second other embodiment of the present invention, a video signal which is not a letterbox signal or a letterbox signal of FIG. The waveform (a) of each portion when the main image portion video signal is input and the waveform (b) of each portion when the boundary between the main image portion and the non-image portion is input will be described.

Signal (l + 1) input to the input terminal 31
Is input to the delay circuit 32 whose delay amount is one line period, and becomes the signal 1 with a delay of one line period. When the input signal is a video signal that is not a letterbox signal or the main image portion of the letterbox signal, the boundary detection circuit 33 that detects the boundary between the main image portion and the non-image portion does not output the determination signal. in this case,
Normal processing is performed using the signals of (l + 1), 1 for the present and past two lines. The subtractor 34 subtracts the output signal l of the delay circuit 32 from the input signal (l + 1).
The output of the subtractor 34 is limited to the color signal band by the BPF 35. The output of the BPF 35 is selected by the switch 36 controlled by the boundary detection circuit 33, and the output terminal 37 is selected.
To obtain the color signal C. The color signal C is subtracted from the input video signal by the subtractor 38 to obtain the luminance signal Y at the output terminal 39.

When the input signal is the boundary between the main picture part and the non-picture part of the letterbox signal located at the two upper and lower parts of the screen, the boundary detection circuit 33 outputs a judgment signal. At the boundary, signal processing is performed using one line of the main picture portion of the two lines. In FIG. 4B,
The upper boundary signal is shown as the input signal.

When the boundary detection circuit 33 determines that the boundary is the upper boundary, the switch 40 selects the input signal (l + 1) and inputs it to the BPF 41. When the boundary detection circuit 33 determines that the boundary is the lower boundary, the switch 40 causes the delay circuit 32 to operate.
The output signal 1 of is selected and input to the BPF 41. BPF
Reference numeral 41 limits the present signal (l + 1) or the past signal 1 which is the output of the switch 40 to the color signal band, and performs the processing within one line. That is, when 1 line out of 2 lines is a non-image portion signal, the Y / C separation processing in the horizontal direction is performed on the remaining 1 line of the main image portion. The boundary detection circuit 33 also controls the switch 36 to select the output of the BPF 41 that has been separated by Y / C for one line at the boundary between the main image portion and the non-image portion, and output the color signal C. The color signal output C is subtracted from the input video signal by the subtractor 38 to obtain the output luminance signal Y.

The (l + 1) line in FIG. 4B is the main picture portion signal immediately after the non-picture portion section. The l line is a non-image portion signal immediately before the main image portion section. The mutual signals have no correlation, and the conventional example cannot correctly perform Y / C separation. However, in this embodiment, as shown in FIG. 4B, the Y / C separation can be correctly performed.

In this embodiment, two lines are not processed at the boundary between the main picture part and the non-picture part of the letterbox signal.
At the boundary, in-line processing using one line of the main image portion is performed. By switching between the 2-line signal processing and the 1-line signal processing, erroneous signal processing is not performed even at the boundary between the main image portion and the non-image portion, and signal processing without image quality deterioration can be performed.

The delay circuit 32 of the embodiment shown in FIG. 3 can obtain the same effect even if the delay amount is one field period. Further, the boundary detection circuit 33 may detect the boundary between the main image part and the non-image part of the letterbox signal, and further detect whether it is the upper boundary or the lower boundary. It doesn't matter.

A third embodiment of the present invention when applied to a 3-line Y / C separation circuit will be described with reference to the circuit configuration diagram of FIG. When the signal (x + 1) input to the input terminal 50 is a video signal that is not a letterbox signal or the main image portion of the letterbox signal, the boundary detection detection circuit 51 that detects the boundary between the main image portion and the non-image portion determines No signal is output. In this case, normal processing is performed using the signals for the current, past, and future three lines.

The input signal (x + 1) is input to the BPF 52a, the delay circuit 53a having a delay amount of one line period, and the boundary detection circuit 51, respectively. The input signal (x + 1) becomes the signal x delayed by one line period by the delay circuit 53a.
The signal x is input to the BPF 52b, the delay circuit 53b that sets the delay amount to one line period, and the subtractor 54, respectively. The signal x is delayed by one line period by the delay circuit 53b to become the signal (x-1). Signal (x-1) is BPF52c
To enter. The signal (x + 1) is a future signal, x is a current signal, and (x-1) is a past signal, and processing is performed using signals of three lines.

The signals on each line are BPFs 52a to 52c.
The respective color signal bands are extracted by. The outputs of the BPFs 52a and 52c are inverted by inverters 55a and 55b, respectively, in order to match the phase with the signal of the current line.
The output of the inverter 55a is the future color signal component, and the BPF 52b.
Is the current color signal component, and the output of the inverter 55b is the past color signal component. The future and present color signal components are added by the adder 56a and averaged. Similarly, the current and past color signal components are added by the adder 56b and averaged.

Five color signal components of present, past, future, present and future average, and present and past average are input to a 5-tap median filter 57. The 5-tap median filter 57 is a filter that extracts the third largest signal from the five signals. The 5-tap median filter 57 extracts the color signal component and inputs it to the switch 58. The switch 58 is controlled by the boundary detection circuit 51, and in the case of normal processing, the 5-tap median filter 5 is used.
7 output is selected and output. The output of the switch 58 becomes an output color signal. Further, the color signal C is subtracted from the current signal x by the subtractor 54 to obtain the output luminance Y.

If there is a non-image portion signal even in one line among the three lines, the main image signal and the non-image portion have no correlation, and therefore normal processing cannot be performed correctly. The boundary detection circuit 51 outputs a determination signal at the boundary between the main image part and the non-image part of the letterbox signal where the input signal is located at two positions above and below the screen. At the boundary, signal processing is performed using 2 lines of the main image part among 3 lines.

The case where the boundary detection circuit 51 determines that the boundary is the upper boundary, that is, the case where only (x-1) of the three line signals is the non-image part line will be described. The switch 59a selects the future color signal component, and the switch 59b selects the average of the present and future color signal components. The outputs of the switches 59a and 59b and the three signals of the current color signal component are input to the 3-tap median filter 60.

The case where the boundary detection circuit 51 determines that the boundary is the lower boundary, that is, the case where only (x + 1) of the three line signals is the non-image part line will be described. The switch 59a selects a past color signal component, and the switch 59b selects an average of the present and past color signal components. Switch 59a,
The output of 59b and the three signals of the current color signal component are input to the 3-tap median filter 60.

The 3-tap median filter 60 selects and outputs the second largest signal among the three inputs. The output of the 3-tap median filter 60 is input to the switch 58. The switch 58 is controlled by the boundary detection circuit 51, and selects and outputs the output of the 3-tap median filter 60 at the boundary between the upper and lower non-image areas. The output of the switch 58 becomes the color signal C. Further, the color signal output is subtracted from the current signal x by the subtractor 54, and the luminance signal Y is output. That is, when 1 line out of 3 lines is a signal of a non-image portion, Y / C separation processing is performed on the remaining 2 lines of the main image portion.

In this embodiment, at the boundary between the main picture part and the non-picture part of the letterbox signal, processing is not performed in 3 lines,
Processing using two lines of the main image part is performed. By switching between the 3-line signal processing and the 2-line signal processing, erroneous signal processing is not performed even at the boundary between the main image portion and the non-image portion, and signal processing without image quality deterioration can be performed.

The same effect can be obtained even when the delay amount of the delay circuits 53a and 53b is one field period. Further, the boundary detection circuit 51 may detect the boundary between the main image portion and the non-image portion of the letterbox signal, and further detect whether it is the upper boundary or the lower boundary. It doesn't matter.

A fourth embodiment of the present invention applied to a noise reduction circuit will be described with reference to FIG. The signal (y + 1) input to the input terminal 61 is input to the delay circuit 62 whose delay amount is one line period and becomes the signal y delayed by one line period. When the input signal is a video signal that is not a letterbox signal or the main image portion of the letterbox signal, the main image portion / non-image portion boundary detection circuit 63 does not output the determination signal. In such a case, normal processing is performed using the signals for the current and past two lines of (y + 1) and y. The output signal y of the delay circuit 62 is subtracted from the input signal (y + 1) using the subtractor 64 to obtain the line decorrelation component. The output of the subtracter 64 is limited by the limiter 65 to the level of the line decorrelation component. The output of the limiter 65 is input to the coefficient multiplier 66 and multiplied by the coefficient. The switch 67 controlled by the detection signal of the boundary detection circuit 63 selects the output of the coefficient unit 66 and becomes a noise component. This noise component is subtracted from the input video signal using the subtracter 68, and the luminance signal Y from which the noise is removed is obtained at the output terminal 69.

At the boundary between the main picture portion and the non-picture portion of the letterbox signal where the input signal is located at the upper and lower portions of the screen, the boundary detection circuit 63 outputs a judgment signal. At the boundary, noise reduction should not be performed. In FIG. 6, the GND level instead of the noise component is subtracted from the input signal by the subtractor 68 to obtain the output luminance signal.

Here, it is assumed that the (y + 1) line is the main image portion signal immediately after the non-image portion section, and the y line is the non-image portion signal immediately before the main image portion section. When noise reduction is performed between the two, the signals that do not correlate with each other have large line decorrelation components, and components that are not noise are also subtracted. However, erroneous signal processing is not performed by setting the noise component to the GND level at the boundary.

In this embodiment, no signal processing is performed at the boundary between the main picture portion and the non-picture portion of the letterbox signal. By switching between the case where no processing is performed and the normal signal processing, erroneous signal processing is not performed even at the boundary between the main image portion and the non-image portion, and signal processing without image quality deterioration can be performed.

Similar effects can be obtained even when the delay amount of the delay circuit 62 is one field period. Furthermore, the same can be said for processing between a plurality of lines or between a plurality of fields. Further, the boundary detection circuit 63 may detect the boundary between the main image portion and the non-image portion of the letterbox signal, and the circuit configuration is not limited.

Next, another fifth embodiment of the present invention when applied to a cyclic noise reduction circuit will be described with reference to FIG. The signal input to the input terminal 71 is input to the subtractor 72 to subtract a noise component described later. The input signal (z + 1) from which the noise component is subtracted is input to the delay circuit 73 whose delay amount is one line period, and the signal z delayed by one line period is output here. When the input signal is a video signal that is not a letterbox signal or the main image portion of the letterbox signal, the main image portion / non-image portion boundary detection circuit 74 does not output the determination signal. In this case, normal cyclic noise reduction processing is performed using the current and past two lines of signals of (z + 1) and z. The subtractor 75 is used to output the delay circuit 7 from the input signal (z + 1) from which the noise component has been subtracted.
The output signal z of 3 is subtracted to obtain the line decorrelation component. The output of the subtractor 75 is limited by the limiter 76 to the level of the line decorrelation component. The output of the limiter 76 is
It is input to the coefficient unit 77 and multiplied by the coefficient. A switch 78 controlled by the boundary detection circuit 74 selects the output of the coefficient multiplier 77 to be a noise component. This noise component is subtracted from the input video signal by the subtractor 72, and the luminance signal Y from which noise has been removed is output from the output terminal 79.

In the case where the input signal is the boundary between the main image part and the non-image part of the letterbox signal at the upper and lower portions of the screen, the boundary detection circuit 74 outputs a determination signal. At the boundary, noise reduction is not performed, and only the writing process in the delay circuit 73 is performed. The subtractor 72 subtracts the GND level instead of the noise component from the input signal to obtain the output luminance signal.

Here, it is assumed that the (z + 1) line is the main image portion signal immediately after the non-image portion section, and the z line is the non-image portion signal immediately before the main image portion section. When noise reduction is performed between the two, the signals that do not correlate with each other have large line decorrelation components, and components that are not noise are also subtracted. However, erroneous signal processing is not performed by setting the noise component to the GND level at the boundary.

The same effect can be obtained when the delay amount of the delay circuit 73 is one field period. Boundary detection circuit 7
4 may detect the boundary between the main image part and the non-image part of the letterbox signal, and the circuit configuration does not matter.

In this embodiment, the noise reduction process is not performed at the boundary between the main image part and the non-image part of the letterbox signal, but only the writing process to the delay circuit is performed. By switching the normal signal processing and the case where only the writing processing is performed in the delay circuit, erroneous signal processing is not performed even at the boundary between the main image portion and the non-image portion, and signal processing without image quality deterioration can be performed.

With the input letterbox signal in each of the above-mentioned embodiments, the same effect can be obtained even in the case of the EDTV-2 signal.

[0045]

As described above, according to the video signal processing circuit of the present invention, it is possible to perform signal processing without image quality deterioration even at the boundary between the main image portion and the non-image portion with a simple structure.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram for explaining an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram for explaining another first embodiment of the present invention.

FIG. 3 is a circuit configuration diagram for explaining another second embodiment of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operation of FIG.

FIG. 5 is a circuit configuration diagram for explaining another third embodiment of the present invention.

FIG. 6 is a circuit configuration diagram for explaining another fourth embodiment of the present invention.

FIG. 7 is a circuit configuration diagram for explaining another fifth embodiment of the present invention.

FIG. 8 is a circuit configuration diagram for explaining a conventional example.

FIG. 9 is a signal waveform diagram for explaining the operation of FIG. 8;

FIG. 10 is an explanatory diagram for explaining a letterbox signal.

[Explanation of symbols]

12, 24, 33, 51, 63, 74 ... Boundary detection circuit,
13, 18, 25, 28 ... Signal processing circuit, 14, 22,
23, 32, 53a, 53b, 62, 73 ... Delay circuit,
15, 17, 26, 27, 36, 40, 58, 59a,
59b, 67, 78 ... Switch, 34, 38, 54, 6
4, 68, 72, 75 ... Subtractor, 35, 41 ... BPF,
52a to 52c ... BPF, 55a, 55b ... Inverter, 5
6a, 56b ... Adder, 57 ... 5-tap median filter, 60 ... 3-tap median filter, 65, 76
... Limiter, 66, 77 ... Coefficient unit.

Claims (8)

[Claims] 1. A video signal processing device for performing addition / subtraction processing between a plurality of horizontal lines or a plurality of fields, in the case of a letterbox type input video signal, a boundary between a main picture part and a non-picture part of the video signal is set. A video signal processing device comprising: a detecting means; and a means for controlling so as to perform signal processing only on a main image portion when the detecting means detects a boundary. 2. A video signal processing apparatus for performing addition / subtraction processing on 3 lines (or 2 lines) of a plurality of horizontal lines, in the case of a letterbox type input video signal, a main image part and a non-display part of the video signal. Video signal processing comprising means for detecting a boundary of an image portion, and means for performing signal processing of two horizontal lines (or one horizontal line) of the main image portion when the means detects the boundary. apparatus. 3. The video signal processing device according to claim 1, wherein the signal processing of the main image section is to perform Y / C separation. 4. The video signal processing device according to claim 1, wherein the signal processing of the main image section is for performing noise reduction. 5. The video signal processing device according to claim 1, wherein the signal processing of the main image portion is vertical emphasis. 6. A video signal processing device for performing addition / subtraction processing between a plurality of horizontal lines or a plurality of fields, in the case of a letterbox type input video signal, a boundary between a main picture part and a non-picture part of the video signal is set. And a means for stopping the operation of a noise reduction circuit for removing noise of the input video signal and / or an emphasis circuit for performing vertical emphasis when the boundary is detected by the means. Video signal processing device. 7. The video signal processing device according to claim 6, wherein when the noise reduction circuit is of a cyclic type, the circulation of the input video signal in the non-picture part is stopped. 8. The video signal processing apparatus according to claim 1, wherein the input video signal is an EDTV-2 system signal.